Aircraft: COMMERCIAL FIXED WING
Phase of flight: Parked
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Other / Unknown

We had a normal boarding procedure; I was Flight Attendant (FA) 3 at door 2 left. In flight we had periods of bumps; the last 20 minutes we experienced moderate to severe turbulence; Flight Attendant X and I experienced it. FA X sat herself down on the aisle while I grabbed on to the seats. FA Y made the announcement; 'flight attendants take your jump seats.' We both then proceeded to our jump seat. FA X arrived first and literally slid over to door 2 left; I took the 2 right jump seat. We strapped in and sat there until landing. As I stated earlier our original jump seats were switched due to the quick seating; and since FA X arrived at the jump seat first; she took 2 left.Upon landing; FA Y made his announcement; 'flight attendants disarm doors for arrival; cross check and stand by for all call.' We both got out of the jump seat and went to disarm the doors for the respective jump seat position; not talking; only concerned with disarming; I proceeded to disarm door 2 right.I looked over to cross check FA X and I noticed the red light in the window for slide armed and also the fact that the 'RME' was still lined up with the A and D for 'ARMED'. FA X then stated that she had lifted the door handle. FA X had some deliberation over whether or not she should attempt to push the door handle down; at that point the door was not open yet. I said nothing; and I cannot say if the door was open at all; only that I noticed the red armed light and armed lever flush to the door. The door opened and the slide inflated. I took FA X's shoulder and told her to stay clear of the door.We then heard the All Call and I answered the phone; FA Y stated his doors were disarmed crosschecked. I answered;'2 left slide deployed; 2 right disarmed and cross checked'. FA Y asked if the door had been opened and the slide deployed. I repeated that yes; 2 left in fact had been open and the slide was deployed. FA X and I both then looked out the door to check if anyone had been hurt; fortunately no one was near the aircraft. We waited by our doors until the passengers had all deplaned; the passengers did not know of the slide deployment to our knowledge as we were both quiet at this point. FA X stated that she was extremely tired after waking up for our early morning call outs for the last 3 days. She also wondered if she had too much going on in her head which may have impeded her from making the correct decision to disarm the door.FA X stood in front of her door and looked at me then the door and said something to the effect that she could not believe she had opened the door; didn't know if she should have held on to the handle and tried to close the door again and stated again that she could not believe what just transpired. FA Y came back and we attached the black and yellow strap to the door frame as a security measure. Then the pilots came back and took over from there on the analysis of the door. We deplaned and went to our hotel. Air carrier Flight Attendant reported an inadvertent deployment of an evacuation slide.